Settlement patterns and temporal successions of coral reef cryptic communities: implications for evaluating diversity using Autonomous Reef Monitoring Structures (ARMS)

Abstract

Abstract Autonomous Reef Monitoring Structures (ARMS) are used worldwide to assess cryptic diversity, especially on coral reefs. They were developed as standardised tools, yet conditions of deployment, such as immersion duration and/or deployment and retrieval seasons, vary among studies. Here we studied temporal and seasonal variability in coral reef cryptic communities sampled with 15 ARMS on a single coral reef slope site at Reunion Island, Southwest Indian Ocean. Settlement patterns and temporal succession of Eukaryote communities were investigated across three immersion times (6 months, 1 year, 2 years), two immersion seasons (hot vs. cool) and three fractions (500–2000 µm, 106–500 µm, sessile) using two genetic markers (18S, COI). Both markers detected different taxa with different resolutions, but broadly similar patterns of community composition and structure. While OTU diversity of communities did not change with immersion time and season, these parameters significantly affected community structure and composition. Our results evidenced a decrease of the similarity of ARMS communities with immersion time, due to a high turnover of early colonisation stages followed by an increase in the differences in OTU richness. The small proportion of OTUs assigned at phylum level highlights the uniqueness of the Mascarene cryptobiome.